Transferases in Polymer Chemistry - Enzymatic Polymerisation - page 22

1 Introduction

Enzymatic polymerizations are an emerging research area with not only enormous
scientific and technological promise, but also a tremendous impact on environmental
issues. Biocatalytic synthetic pathways are very attractive as they have many advan-
tages, such as mild reaction conditions, high enantio-, regio- and chemoselectivity,
and the use of nontoxic natural catalysts.
Transferases (enzyme classification, class no. 2) are enzymes that catalyze reac-
tions in which a group is transferred from one compound to another. Groups that are
transferred are Cl, aldehydic or ketonic residues, acyl, glycosyl, alkyl, nitrogenous,
and phosphorus- and sulfur-containing groups [ 1 ] . Of the three classes of enzymes
used in polymer science so far, transferases are the least applied class of biocata-
lyst. Despite their potential for synthesizing interesting polymeric materials many
transferases are very sensitive biocatalysts, which prevents their isolation on a larger
scale and/or their use for synthesizing polymers on a reasonable scale.
The enzyme class of transferases is subdivided into nine subclasses:

EC 2 Transferases
EC 2.1 Transferring one-carbon groups
EC 2.2 Transferring aldehyde or ketonic groups
EC 2.3 Acyltransferases
EC 2.4 Glycosyltransferases
EC 2.5 Transferring alkyl or aryl groups, other than methyl groups
EC 2.6 Transferring nitrogenous groups
EC 2.7 Transferring phosphorus-containing groups
EC 2.8 Transferring sulfur-containing groups
EC 2.9 Transferring selenium-containing groups

This review focuses on acyl- and glycosyltransferases and transferases that transfer
alkyl or aryl groups, other than methyl groups (EC 2.3, EC 2.4, and EC 2.5) as in
these classes can be found interesting examples for the polymer scientist.
Acyltransferases are, for instance, able to synthesize biological polyesters
with properties comparable or sometimes even exceeding polymers based on
petrochemical-derived monomers. Acyltransferases are also frequently used to
modify macromolecules in food and non-food applications.
For the synthesis of highly defined polysaccharides, glucosylsaccharides are the
only option available. Specialized oligo- and polysaccharides for food and medical
applications can be synthesized, and also hybrid structures with non-natural macro-
molecules or surfaces.
Prenyltransferases are responsible for the synthesis of cis -polyisoprene in natural
rubber particles but can also be used to synthesize polyisoprenes in vitro.